In photography, camera flashes from an LED array can cause undesirable color temperature disruptions. Conventional camera flash systems with color adjustable flash units are known. For example, U.S. Pat. No. 8,817,128, which is incorporated by reference, discloses adjusting illumination for controlling color temperature in a camera flash system. Data that corresponds to the ambient light of a physical environment is collected, such as by a color temperature meter included in the camera. The ambient light has a distribution of color temperatures that cycle over a fixed time period. When a flash request is received, a time cycle is calculated to determine when the flash unit will flash. A color temperature is identified from a distribution of color temperatures, and a color temperature is predicted for ambient light that is present in the physical environment when the flash unit flashes. The color temperature of the flash unit is then set to the identified color temperature.
Color temperature selection for an array of LEDs is also known. For example, U.S. Pub. 2005/0168965, which is incorporated by reference, describes an array of LEDs used in a flash device. In this disclosure, light flashes towards a subject in a photographic scene using an LED matrix array, such that individual lighting fields differ from one another. A selective excitation circuit is used for selectively illuminating the LEDs so as to produce a projected flash light, which differs in intensity.
Segmented LED arrays with adaptive flash features are also known. These LED arrays allow flash systems to illuminate a scene more homogenously, without uneven bright and dark regions. Adaptive flash LEDs can be used to avoid overexposure by selective dimming and/or enhancing of certain LED segments within the LED array. To ensure satisfactory contrast in a scene illumination, optics can effectively image the LED array onto a selected scene. However, for white LEDs, color variations still exist due to local over-conversion of light. This over-conversion can produce yellow light due to locally thicker phosphor layers in the LED array. In segmented LEDs, during selective illumination a single LED of the LED array is illuminated while a directly adjacent or neighboring LED is not illuminated. In monolithic matrix LED arrays, a sapphire or phosphor layer covers the active light emission sites as a single piece or layer. This arrangement leads to light deflecting inside the matrix blocks. Due to different extraction efficiencies (i.e. how much blue or phosphor converted light is projected from the LED), a single illuminated LED segment may generally cause a yellow rim in adjacent switched off LED segments.
It would be desirable to provide an LED array that reduces or eliminates the undesirable color error in an LED array.